Spin transition during H2O2 formation in the oxidative half-reaction of copper amine oxidases

Rajeev Prabhakar, Per E M Siegbahn, Boris F. Minaev, Hans Ågren

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Dioxygen reduction in the oxidative half-reaction of copper amine oxidases (CAOs) has been studied quantum chemically using the hybrid density functional theory (B3LYP). The reductive activation of dioxygen is a spin-forbidden process for which substantial kinetic O-18 (but no deuterium) isotope effects have been found experimentally. The proposed mechanism was divided into three steps, and the last step was studied for two different potential energy surfaces: the quartet and the doublet surfaces. It is suggested that dioxygen reduction occurs through a spin transition that is induced by the exchange interaction between the unpaired spins of the Cu(II) ion and the O 2- anion. The step involving this spin transition is suggested to be rate-limiting, which gives a rationalization for the puzzling experimental results when copper is substituted for other metals. The spin transition is triggered by the calculated vibronic perturbation of 5.4 (kcal/mol) Å-1, which leads to a very fast rate of 8 × 1010 s-1 for the spin transition. However, since the spin transition occurs at a calculated energy that is 18-20 kcal/mol higher than that of the reactant, this step could still be rate-limiting. The difference in the O-O bond distance between the resting state (free dioxygen) and the point of the spin transition provides an explanation for the oxygen isotope effect.

Original languageEnglish
Pages (from-to)13882-13892
Number of pages11
JournalJournal of Physical Chemistry B
Volume108
Issue number36
DOIs
StatePublished - Sep 9 2004
Externally publishedYes

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Amine Oxidase (Copper-Containing)
oxidase
Isotopes
Amines
amines
Oxygen
Copper
copper
Potential energy surfaces
Exchange interactions
Deuterium
Density functional theory
Negative ions
Oxygen Isotopes
Chemical activation
Kinetics
Ions
Metals
isotope effect
Anions

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Spin transition during H2O2 formation in the oxidative half-reaction of copper amine oxidases. / Prabhakar, Rajeev; Siegbahn, Per E M; Minaev, Boris F.; Ågren, Hans.

In: Journal of Physical Chemistry B, Vol. 108, No. 36, 09.09.2004, p. 13882-13892.

Research output: Contribution to journalArticle

Prabhakar, Rajeev ; Siegbahn, Per E M ; Minaev, Boris F. ; Ågren, Hans. / Spin transition during H2O2 formation in the oxidative half-reaction of copper amine oxidases. In: Journal of Physical Chemistry B. 2004 ; Vol. 108, No. 36. pp. 13882-13892.
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